It is proposed to continue operating a facility for analytical, bio-medical mass spectrometry. The major sub-divisions of the resource activity will be (1) basic research in mass spectrometry and gaseous ion chemistry, (2) instrumental and methodological developments of applications of mass spectrometry to biomedical problems, and (3) analytical service work. The basic research activities will be concerned with (1) study and development of negative chemical ionization mass spectrometry and (2) study and developmnt of fission fragment ionization mass spectrometry and/or ion bombardment desorption mass spectrometry and/or laser desorption mass spectrometry. After the development of any of these desorption mass spectrometers it will be placed in service making biomedical analyses. Several collaborative projects will be undertaken. Two examples of these are: (1) determination of the effect of drug-drug interactions on metabolism of methadone and other substances, and (2) determination of pool size and turnover in newborns of 26 - hydroxycholesterol and bile acid pool sizes in "pre-gallstone" populations.